I built this bench top 35 years ago from a solid core door. It has worked well for me but the bench dog holes are too worn to use my Holdfast clamps. The holes have become elongated from using these clamps. I want to know if you have any better suggestions on repairing them. I thought I would turn a hard maple dowel like in the drawing and then use my old drill guide with forestner bits to enlarge the hole and epoxy the dowel repair in. My question, other than is there a better way, is should I make the dowel larger. The wood I have is plenty large to I can make the repair dowel any size.
I would just turn the maple straight, then not drill all the way out the bottom. l would leave about 1/8", then tape the underside to contain any sagging epoxy.
I would prime the inside of the hole with straight epoxy, then mix up some thickened to fill the gaps in the particle board core. Do you have some silica for thickening?
there isn't any particle board. It's a solid Oak Door. the reason I put a step in is to give some more glue surface but maybe I can make the step smaller and make the bottom hole just a hair smaller than the top hole. I was worried about not having enough "meat" in the wood but in reality the maple will be backed up with solid Oak. Yes I will tape on the bottom to keep the epoxy from running out.
Even with your drill guide staring forestner bits with out a center and getting a clean entry will not be easy with a high risk of the bit wandering off center. I say turn a plug to fit the hole and glue it in place then drill the hole and reduce the plug into sawdust.
I would be tempted to make the plug both at the top and bottom if I had the big forestner bits.
I see no advantage in making the new hole on the lathe drill it in the bench after the glue is dry.
I am going to clamp drill guide to the workbench which I hope will work. I can drill the 3/4" hole in the blank on the lathe so won't have to drill that hole. I think I only have 3 or 4 that are worn bad enough to need this repair.
I'm guessing the benchtop is long grain, the dowel as in the diagram end grain. I would give some though to making a rectangular mortise in the benchtop and matching long grain plug. Drill at least most of the way through the plug on the drill press, glue the plug in place, then finish drilling through the plug.
I actually thought about the grain direction last night. I can easily turn the plug side grain. I originall.thought about cutting a rectangular hole a little ways down and filling with a matching block but the damaged holes are tapered most.of the way down and need to.be filled.
A lot of the advise I see here, and your drawing of the plug, are specific to dog holes only used for holding dogs, tools and work lights. The requirements for dog hols used for holdfast are a lot more stringent, since the holdfasts put an immense amount of lateral pressure at two points: the top of the hole at the back of the holdfast, and the bottom of the hole at the front of the holdfast. Of course, these points change as the holdfast is rotated to hold stuff at different locations on the bench top. Therefore, my recommendations are as follow:
Drill a large diameter hole all the way through the bench top. This will get rid of any wallowing bt the holdfast.
Use hard maple for the plug, it deforms and splits much less than oak. Turn it in the shape of a cylinder, without any steps, with the grain orientation you would use for a bowl. It would also probably help a little to align the growth rings of the plug with the growth rings of the bench top. This alignment, of course would need to be done before mounting the plug for turning. This will stress the wood of the bench top much less with the change of the seasons. Make it as long as the thickness of the bench top, unless the bench top is more than about 3" thick. Holdfasts don't hold as well in very thick bench tops because they aren't tilted at as large an angle, and the pressure they develop against the sides of the dog hole is not as great.
Replace that junk cast iron holdfast with one or two by Gramercy Tools, and consider adding a doe's foot (shop made) to your work holding arsenal.
Another option (similar to the steel bushing idea) is to epoxy copper pipe (3/4" dia) liners in your existing dog holes. You may need to file a bit to make the pipe sections fit. I got this idea from someone on this forum about 17 years ago when I was building my workbench top out of 4 layers of plywood, skinned with hardboard. It has worked well for me over all these years. I am now thinking about upgrading the top to maple, and will likely do the same with the dog holes.
